The chemical 5-amino-2, 3-dihydro-phthalazinedione, better known as luminol, is

Question

The chemical 5-amino-2, 3-dihydro-phthalazinedione, better known as luminol, is used by forensic scientists in analyzing crime scenes for the presence of washed away blood. Luminol is so sensitive that it can detect blood that has been diluted 10,000 times. A basic solution of luminol is often sprayed onto surfaces that are suspected of containing minute amounts of blood. Luminol has a molecular weight of 177 g/mol. The forensic technician at a crime scene has just prepared a luminol stock solution by adding 17.0 g of luminol into a total volume of 75.0 mL of H_2O. What is the molarity of the stock solution of luminol? Express your answer with the appropriate units. molarity of luminol solution = g/mol Before investigating the scene, the technician must dilute the luminol solution to a concentration of 2 00 times 10^-2 M. The diluted solution is then placed in a spray bottle for application on the desired surfaces. How many moles of luminol are present in 2.00 L of the dated spray? Express your answer with the appropriate units. moles of luminol =

Explanation / Answer

Part A

Luminol has molecular formula C8H7N3O2 and has molecular weight = 177.16 g/mol.

Hence 177.16 g of Luminol = 1 mole of luminol

16 g of luminol = 1x 16 / 177.16 = 0.903 mol of luminol.

Now 75 ml water solution contains 0.903 mol of luminol

1000 ml water contains 0.903 x 1000/75 =12.04 mol of luminol

Hence molarity of luminol solution = 12.04 mol / L

Part B

Molarity = 2.00 x 10-2 M = 2.00 x 10-2 mol / L , volume = 2.00 L

Moles of luminol = molarity x volume = 2.00 x 10-2 x 2.00 mol = 4 x 10-2 mol

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